Joining and rotating several kitchen doors
Join all the meshes you don't want to animate, like floors and walls, with ctrlJ. 

About the doors: Keep them as separate objects. You can parent them to the house object (ctrlP > Object) so that when you'll move the house on your scene they will follow.

You can't use the Pivot Point of the 3D View to animate them, because it's not taken into account in animations, so come back to Median Point for example. You have to use bones, or, even simpler, use origin point:

In Edit mode Select the face where you want the rotation axis to be (ie hinge of the door), press shiftS > Cursor to Selected, go back in Object mode and press shiftctrlaltC > Origin to 3D Cursor. Now the pivot point will be correct.